<snip>
my client wants to put up a copy of his passport in there
so that if he loses it whilst flying around the world he can just
download a copy from anywhere to help with sorting out a new one.
</snip>
Look at how eCommerce sites do it. If you forget your password, you enter
your email address and the password for that email address is sent. Maybe
you should look at writing a program that he can login, and then request
the file be sent to his email (hotmail or something). Does he login to
email remotely? How about just keeping it in there for good?
-Ron